Effect of isotope enrichment on performance of lead-lithium blanket of inertial fusion reactor

Abstract

Simulation studies on neutron transport and material activation for lead-lithium (Pb-17Li) blanket of the inertial fusion reactor "KOYO-FAST" were performed with the PHITS code and the EASY 2005 code. Tritium breeding ratio (TBR) and productions of harmful radioactive isotopes 210Po and 203Hg in the blanket are made clear. The blanket performances improved by enrichment of stable isotope (6Li, 204Pb, 206Pb or 207Pb) are also made clear. The TBR is 1.28 for the blanket with a natural Pb-17Li alloy. The large TBR is allowed because of large blanket space in the reactor chamber. The TBR reaches 1.64 when 6Li is enriched to 90%. In this case, intermediate and thermal neutrons, that are necessary to produce 210Po and 203Hg, are preferentially captured by the 6Li (n, α) T reaction. Then, the productions of 210Po and 203Hg are mitigated. The enrichment of 204Pb leads to a small TBR, because neutrons are captured by 204Pb due to its large cross section for (n. γ) reaction. The TBR of 206Pb or 207Pb enriched Pb-17Li is more or less the same with that of the natural Pb-17Li. In these cases, the productions of 210Po and 203Hg are slightly mitigated because of the removal of 208Pb and 204Pb from the blanket.